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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Helium and minor ions in the corona and solar wind - Dynamics and charge states

A theoretical model of the acceleration region of the solar wind with major species (p, alpha, e) and minor ions (e.g., He-3, C, O, Mg, Si) is presented. Observed n(e)-profiles and the equations of continuity and momentum are used to calculate profiles of T, n, and u for all species, as well as charge states of minor ions. The disagreement of the results of a pure p-e model with observations is discussed in some detail, and it is shown that a model consistent with observations both in the corona and at 1 AU requires a finite abundance of He(2+). This model predicts a strong enhancement of He/H in the lower corona. The results for the frozen-in charge states in the p-alpha-e model are in agreement with measurements in the low speed solar wind, especially for the well determined pair O(6+)/O(7+). Finally, a model for a coronal hole is investigated and it is found that wave pressure is necessary to model successfully the observed solar wind speeds and abundances. Although various simplifying assumptions had to be introduced, care was taken to ensure that the model remains physically consistent, i.e., that the same physics is used for the major species as well as the minor ions.

Buergi, A.↗
NASA NTRS1952

Solutions of laminar-boundary-equations which result in specific-weight-flow profiles locally exceeding free-stream values

Revised solutions of the laminar-boundary-layer equations for cases which involved cooling at the wall combined with large pressure gradients in the main stream produced specific-weight-flow profiles which locally exceeded free-stream values. Heat-transfer and friction coefficients, boundary-layer thicknesses, and velocity, temperature, and specific-weight-flow distributions resulting from the revised solutions are presented for Euler numbers of 0.5 and 1, stream-to-wall temperature ratios of 2 and 4, and cooling-air flow rates through porous walls designated by flow parameters of 0, -0.5, and -1.

HEAT TRANSFER, AERODYNAMIC↗
NASA NTRS2000

Radar Images of the Kuiper Quadrangle (Mercury) from Goldstone Radar Data

We have assembled all currently processed radar data from 1989 to 1998 into crude images covering the Kuiper (H6) region on Mercury. The data used were taken to support the ephemeris improvement and gravitational physics programs; however, the resolution is good enough in some cases to make north/south ambiguous images that show some features that can be identified with the Mariner 10 features. Topography profiles along the apparent equator are also available; some of these profiles show ridges and rills as well as crater depths and diameters. The combination of the optical imaging and the radar imaging can be helpful in understanding similar features in radar images of the optically unimaged hemisphere.

Jurgens, R. F.↗
NASA NTRS1978

Approximate line shapes for hydrogen

Two independent methods are presented for calculating radiative transport within hydrogen lines. In Method 1, a simple equation is proposed for calculating the line shape. In Method 2, the line shape is assumed to be a dispersion profile and an equation is presented for calculating the half half-width. The results obtained for the line shapes and curves of growth by the two approximate methods are compared with similar results using the detailed line shapes by Vidal et al.

Sutton, K.↗
NASA NTRS2000

Characterization of Vertical Ozonesonde Measurements in Equatorial Regions Utilizing the Cooperative Enterprise SHADOZ

Vertical ozone profiles between the Equator and 10 S latitude available from the Southern Hemisphere Additional Ozone (SHADOZ) program provide consistent data Ozone sets from up to 10 sounding locations. SHADOZ designed to provide independent ozone profiles in the tropics for evaluation of satellite ozone data and models has made available over 600 soundings over the period 1998-1999. These observations provide an ideal data base for the detailed description of ozone and afford differential comparison between sites. TOMS total ozone when compared with correlative integrated total ozone overburden from the sondes is found to be negatively biased when using the classical constant mixing ratio procedure to determine residual ozone. On the other hand, the climatological method proposed by McPeters and Labow appears to give consistent results but is positively biased. The longer then two years series of measurements also was subjected to harmonic analysis to examine data cycles. These will be discussed as well.

Schmidlin, F. J.↗
NASA NTRS1975

The measurement of shear stress and total heat flux in a nonadiabatic turbulent hypersonic boundary layer

Turbulent shear stress and direct turbulent total heat-flux measurements have been made across a nonadiabatic, zero pressure gradient, hypersonic boundary layer by using specially designed hot-wire probes free of strain-gauging and wire oscillation. Heat-flux measurements were in reasonably good agreement with values obtained by integrating the energy equation using measured profiles of velocity and temperature. The shear-stress values deduced from the measurements, by assuming zero correlation of velocity and pressure fluctuations, were lower than the values obtained by integrating the momentum equation. Statistical properties of the cross-correlations are similar to corresponding incompressible measurements at approximately the same momentum-thickness Reynolds number.

Mikulla, V.↗
NASA NTRS1975

Turbulence stress measurements in a nonadiabatic hypersonic boundary layer

Turbulent shear stress and direct turbulent total heat-flux measurements have been made across a nonadiabatic, zero pressure gradient, hypersonic boundary layer by using specially designed hot-wire probes free of strain-gauging and wire oscillation. Heat-flux measurements were in reasonably good agreement with values obtained by integrating the energy equation using measured profiles of velocity and temperature. The shear-stress values deduced from the measurements, by assuming zero correlation of velocity and pressure fluctuations, were lower than the values obtained by integrating the momentum equation. Statistical properties of the cross-correlations are similar to corresponding incompressible measurements at approximately the same momentum-thickness Reynolds number.

Mikulla, V.↗
NASA NTRS1973

Nighttime ion composition measurements at the geomagnetic equator

Two ion composition profiles, representative of the nighttime equatorial ionosphere between 90 km and 300 km, are presented. These profiles were obtained by two rocket-borne ion mass spectrometers on a single night for solar zenith angles of 112 deg and 165 deg. For both flights, the principal ion above 200 km is O(+). The downward drift of the atomic ions O(+) and N(+), coinciding with the postsunset lowering of the F2 peak, is observed through an enhancement of the density of O(+) at altitudes above 200 km and N(+) above 240 km. Below the drift region, O(+) and N(+) are observed in concentrations larger than expected. The NO(+) altitude distribution retains its shape throughout the night, and below 210 km, is the principal ion. The behavior of O2(+) can be explained by the O(+), electron density and theoretical neutral nitric oxide concentrations. Light metallic ions, including Mg(+), Na(+), and possibly Si(+), are observed to altitudes approaching 300 km and are affected by vertical drift.

Goldberg, R. A.↗
NASA NTRS2004

The Eastern Pacific ITCZ during the Boreal Spring

The 6-year (1998-2003) rainfall products from the Tropical Rainfall Measuring Mission (TRMM) are used to quantify the Intertropical Convergence Zone (ITCZ) in the eastern Pacific (defined by longitudinal averages over 90 degrees W-130 degrees W) during boreal spring (March-April). The double ITCZ phenomenon, represented by the occurrence of two maxima with respect to latitude in monthly mean rainfall, is observed in most but not all of the years studied. The relative spatial locations of maxima in sea surface temperature (SST), rainfall, and surface pressure are examined. Interannual and weekly variability are characterized in SST, rainfall, surface convergence, total column water vapor, and cloud water. There appears to be a competition for rainfall between the two hemispheres during this season. When one of the two rainfall maxima is particularly strong, the other tends to be weak, with the total rainfall integrated over the two varying less than does the difference between the rainfall integrated over each separately. There is some evidence for a similar competition between the SST maxima in the two hemispheres, but this is more ambiguous, and there is evidence that some variations in the relative strengths of the two rainfall maxima may be independent of SST. Using a 25-year (1979-2003) monthly rainfall dataset from the Global Precipitation Climatology Project (GPCP), four distinct ITCZ types during March-April are defined, based on the relative strengths of rainfall peaks north and south of, and right over the equator. Composite meridional profiles and spatial distributions of rainfall and SST are documented for each type. Consistent with previous studies, an equatorial cold tongue is essential to the existence of the double ITCZs. However, too strong a cold tongue may dampen either the southern or northern rainfall maximum, depending on the magnitude of SST north of the equator.

Gu, Guojun↗
NASA NTRS1992

Formation of quasiparallel Alfven solitons

The formation of quasi-parallel Alfven solitons is investigated through the inverse scattering transformation (IST) for the derivative nonlinear Schroedinger (DNLS) equation. The DNLS has a rich complement of soliton solutions consisting of a two-parameter soliton family and a one-parameter bright/dark soliton family. In this paper, the physical roles and origins of these soliton families are inferred through an analytic study of the scattering data generated by the IST for a set of initial profiles. The DNLS equation has as limiting forms the nonlinear Schroedinger (NLS), Korteweg-de-Vries (KdV) and modified Korteweg-de-Vries (MKdV) equations. Each of these limits is briefly reviewed in the physical context of quasi-parallel Alfven waves. The existence of these limiting forms serves as a natural framework for discussing the formation of Alfven solitons.

Hamilton, R. L.↗
NASA NTRS1987

The quadrupole gravitational lens

An asymmetric lens made of a spherically symmetric galaxy and a quadrupole tidal part allows a very simple pictorial examination of the multiplicity and positions of the images, for any mass density profile. The lens equations can be reduced to one equation in one variable. In the special case of a singular isothermal sphere with a tide (SIST), the lens properties are described by five parameters. Two parameters determine the angular scale and orientation, while three determine the configuration of the images. A comprehensive investigation of the SIST lens is performed, including the variation of the configurations with the parameter values, the critical surfaces in the parameter space, and the extremal solutions. Analytic expressions are derived for the SIST parameters, and additional image positions, in the case when the intensity ratio and positions relative to the galaxy for two of the images are given as input. Quadrupole lenses with a point mass and a pseudoisothermal sphere as the main part are also described in terms of direction diagrams. A direct relation between deflection profile and rotational velocity is derived.

Kovner, Israel↗
NASA NTRS1977

UV stellar occultation measurements of nighttime equatorial ozone

The ultraviolet spectrometer-telescope on Copernicus was used for stellar occultation measurements of atmospheric ozone. Two sets of observations of the target star Beta-Cen were carried out on 26 July 1975 and 13-14 June 1976 at wavelengths from 2550 A to 3100 A. After unfolding of the data, ozone density profiles near the equator within 3 hours of local midnight were obtained at altitudes from 47 to 114 km. A secondary maximum at 97 km has been observed in both sets of data. The ozone density between 47 and 75 km is a factor of 2 to 3 times as large as current models predict. At the lower boundary, about half the ozone destruction should be caused by NOx and ClOx. Above 55 km, virtually all loss is due to HOx. These results suggest an overestimate of HOx and ClOx loss processes or a serious underestimate of the Ox production rate.

Riegler, G. R.↗
NASA NTRS1986

Extinction and visibility measurements in the lower atmosphere with UV-YAG-lidar

With the intention to investigate methods for slant path visibiltiy measurements and to develop information for modelling of extinction profiles in the atmospheric boundary layer, measurements were performed with a lidar based on a YAG-laser. The third harmonic at 355 nm in the ultraviolet was used and thus eye safety problems are avoided. At this wavelength the lens of the human eye is not transparent and the safety distance for the laser is a 50 meters as compared to several km for a corresponding green laser. The lidar is a coaxial system with a turnable mirror system for beam steering. The extinction coefficient at both 355 and 532 nm was measured and the ratio determined. Provided that the wavelength dependence of the aerosol extinction is range independent, the measured extinction profile at 355 nm can be converted to a corresponding profile at 532 nm, which is more relevant for visibility. In order to calculate the extinction profile the lidar equation is inverted by a method, which is based on Klett's method.

Hagard, A.↗